It doesn’t look like anything you’d want in your chest, or the chest of your nearest and dearest, for that matter. Two strange half spheres covered in fabric—Dacron, Silastic and polyurethane—the top torn like petals of some decaying flower, parts of it flecked with strange, brownish stains that could be old blood. Two tubes to nowhere protrude from its lower half. The thing measures 7.5 by 9 by 6.5 inches, though how you would come up with that calculus in a device with such a curious shape is hard to say. If anything, it looks like some ancient, misshapen pair of headphones, but in fact it’s one of the most famous medical devices of all time: the first artificial heart ever implanted in a human being, back in April 1969, in Houston.

It was a strange time. The nation was in turmoil after the assassinations of Robert F. Kennedy and Martin Luther King Jr., the ongoing tragedy of the Vietnam War and President Lyndon Johnson’s announcement that he would not seek re-election. But as riven as the country was by political and racial divisions, there was still a belief in American technological domination. In July 1969, Neil Armstrong became the first man to walk on the moon. That he was guided by a team from NASA, southeast of downtown Houston, is not incidental to this story.

The city was, then, on its way to fulfilling its dream as a technological capital. The first domed sports stadium—a.k.a. the Astrodome—had opened in 1965, and, if Houston wasn’t the energy center of the world yet, it was the center of the oil business, money from which fueled the growth of what was becoming the world’s largest medical center. Then as now, heart disease was the main cause of death, but unlike now, the causes and treatment of heart disease and, specifically, heart attacks remained mysterious. Smoking was still glamorous. Jogging, much less marathon running, had yet to become a thing, as had the whole notion of preventive care when it came to the heart.

What was a thing—the hottest, newest thing—was heart surgery, and two of the most famous doctors in the field were based in Houston: Michael DeBakey, who had, through sheer force of will made Baylor College of Medicine and by extension the Texas Medical Center into a global nexus of medical advancement, and Denton Cooley, a Houston native who had trained at Baltimore’s elite Johns Hopkins and with some of the best surgeons at Brompton Hospital in London. While DeBakey had made his name as a vascular surgeon, a brilliant administrator and a national spokesman for public health, Cooley’s speed and accuracy while operating on the heart itself was becoming the stuff of legend.

The two men were physical and temperamental opposites. DeBakey, the child of Lebanese immigrants who had settled in Baton Rouge, Louisiana, was small and imperious with underlings but charming and erudite among his peers and patrons. Cooley was from a prominent Houston family, so tall and charismatic that successive medical TV shows would spend decades trying to imitate the real thing. The differences between the two men often obscured one profound similarity: towering, relentless ambition.

That ambition was sorely tested when a South African surgeon, Christiaan Barnard, transplanted the first human heart in December 1967 while the most illustrious American cardiac surgeons had to stand aside with very red faces. One of them was Denton Cooley. “Congratulations on your first transplant, Chris. I will be reporting my first hundred soon,” he wrote to Barnard.

In fact, Cooley around that time had felt stymied by a lot of things, including the man who had brought him to Baylor in 1951, Michael DeBakey. DeBakey had a great nose for talent, but he wasn’t the kind of leader who nurtured it. (You can still find doctors who trained under DeBakey and have the shattered nerves to show for it.) Cooley was soon chafing under DeBakey’s management, and, in true Texas style, raised enough money among his oilmen friends to leave DeBakey’s Methodist Hospital for his own Texas Heart Institute, which he founded in 1962.

Barnard’s triumph turned up the heat on what was then, a simmering competition between two surgeons who were probably the most famous in the world, who appeared on the covers of major magazines like Time and Life , and who palled around with famous patients like Jerry Lewis and the Duke of Windsor. Not to be outdone by a foreign doc whose skills were derided in Houston, DeBakey, who had been skeptical of transplants and had been working for years on an artificial replacement for the heart, did a 180 and began to look into heart transplants. He did not invite the participation of Cooley, who had performed the first successful heart transplant in the U.S. in 1968 and had since done more than any other surgeon in the world—17—to join him. (“Maybe it’s immodest of me,” Cooley would later say, “but I thought that since I was the most experienced heart surgeon in the world, I was the one best qualified to perform transplants in Houston.”)

There is some debate—still—about what happened next, but not the ultimate result. Transplantation, it turned out, wasn’t the miracle it had initially appeared to be. By the end of 1968, only three of Cooley’s patients were still alive, and no one knew why. (The introduction of the drug cyclosporine, which suppressed the immune system and allowed the body to accept a new heart, was still about 15 years away.) Prominent surgeons around the world who had similarly lost their transplant patients were calling for a moratorium on the procedure.

Cooley, who had turned up his nose at heart-assist devices coming out of DeBakey’s lab, suddenly developed an interest. He teamed up with an Argentine surgeon and inventor, Domingo Liotta, who had become frustrated by DeBakey’s profound lack of interest in the artificial heart he had been hired to develop. (Experiments on calves had not been promising. The animals looked, according to DeBakey, like “a cadaver from time of implantation” and did not survive for any reasonable length of time.)

So it happened that in 1969, Haskell Karp, a 47-year-old print shop employee from Skokie, Illinois, arrived in Houston under the same coronary death sentence as so many others, only to be told by Cooley, Oz-like, that, why, what he needed was a new heart! But in case one wasn’t immediately available, Cooley also had a new gizmo that could—probably—keep Karp alive until they got one. That was how, on April 4, what is now known as the Cooley-Liotta heart came to beat in Karp’s chest for a total of three days, until he received a transplanted human heart; he died of an infection less than two days later. (Ethical objections were raised because the procedure had been done without formal review.) The device itself now resides in the collections of the Smithsonian's National Museum of American History.

But in the meantime, history was made: Cooley and Liotta had proven that a human being could be kept alive with an artificial heart, launching a quest that lasts to this day. The operation also ignited one of the most famous medical feuds of all time: Once DeBakey found out about the heart purloined from his lab, he fired everyone who worked there and turned Denton Cooley into surgical public enemy No. 1, using his influence to launch local and national investigations of what he termed a theft. Though little came of those, Cooley would later say that the continuing competition that lasted until DeBakey’s death in 2008—Cooley died in 2016—helped to make the Texas Medical Center a global leader in the war on heart disease.

Yet for all the advances made since 1969, there is still no mechanical device that fully can replace the real thing. The human heart remains stubbornly resistant to total replacement, its physical mysteries nearly as challenging as the metaphorical ones that have plagued us since the beginning of time.